I. Field of the Invention
The present invention relates generally to train handling equipment and particularly to car spotting systems for indexing a coupled string or trip of cars through a work station, one or more cars at a time during loading or unloading operations. More specifically, the present invention is directed to providing a more compact drive system that includes additional protection for moving parts. The system employs a chain drive with aligned, vertically disposed drive and idler sprockets which minimize required horizontal space and exposure of drive elements.
II. Related Art
Trains, many containing 100 or more cars of identical or a variety of sizes, have long been acknowledged as desirable and efficient carriers of bulk raw materials such as coal, iron ore, limestone, various finely divided dry bulk agricultural products including grains, etc., and liquid or dry chemicals. These cars are typically filled from above and may be emptied using a rotary car dumper in the case of coal or iron ore. However, gas or liquid filled tank cars or those hauling agricultural products are bottom emptied into stationary material receiving or freight handling equipment such as pipelines, tanks, chutes, conveyor handlers or the like. The cars may be provided with a discharge tube and drain valves or a number of spaced bottom discharging hopper bins or chutes accessing the main storage volume of the car enclosed by sliding discharge gates. These are designed to be precisely positioned at dedicated receiving facilities situated at fixed stations such as grain or coal bins and conveyors positioned beneath the railroad track. Liquid bulk cargo is typically unloaded by connecting outlets to large hoses with associated pumping equipment and opening bottom drain valves. The cargo then being pumped into tanks or tank trucks located near the tracks.
In the discharge operation, a connected train engine roughly positions one end of a string of cars to be unloaded close to the unloading facility. Because train engines are not well suited for indexing or precisely positioning individual cars or sets of cars along the track, train positioning devices or car spotting devices, also known as railroad car progressors or indexers, have been built and operated at fixed stations.
Railroad car indexers of the class of interest include at least one car engaging and propelling strut member or xe2x80x9cdogxe2x80x9d for engaging at least one railroad car in a string or trip of cars and moving the string a given distance along the railroad track. The car engaging members are most often mounted on sliding carriages situated and operated along an auxiliary indexer track or guideway juxtaposed to and in parallel relation to the railroad track in the fixed receiving facility. Fluid operated actuators such as hydraulic cylinders or chains moved by sprockets driven by hydraulic or electric motors supply power for moving the dogs and pulling the railroad cars. U.S. Pat. Nos. 4,006,691, issued to Kacir et al, and 4,354,792, issued to Cornish, show train positioners in the form of cable operated systems with horizontally disposed pulleys that approach the train from alongside the track and including an engaging member arm which engages a car coupler from above.
It is generally known to utilize dogs in the form of heavy vertically pivoting car-engaging arm members which are designed to engage and advance either the railway bogey wheel truck frame or an axle. The dogs are smaller than car coupler engaging arms and are carried by dog carriages which ride alongside on a dog carriage indexer track situated either between the rails of the railroad track to engage the axle or next to the railroad track to engage the bogey truck frame. Bogey frame-engaging dog systems may be further divided into two types. One type includes xe2x80x9clow dogsxe2x80x9d which are dogs that engage the lower portion of the truck frame below the axle; and the other employs xe2x80x9chigh dogsxe2x80x9d which engage the frame at or above the height of the axles. One system using a horizontally disposed chain system to drive high dogs is described in U.S. Pat. No. 5,709,153 to Brandt, assigned to the same assignee as the present invention. That patent is deemed incorporated by reference herein for any purpose.
Most of these indexing systems require a relatively large amount of space alongside the track to accommodate elements,of the systems required to operate the vertically pivoting dogs which pop up to engage the bogey frames or axles of cars and are dropped for storage. They employ horizontal sprocket elements that are exposed to the elements and personnel in the vicinity. Also, many facilities for conducting unloading operations have been constructed with very little horizontal working space alongside the cars to accommodate bogey frame engaging systems. Accordingly, there exists a need for a horizontally compact train indexing system that can be effectively installed and operated in low clearance environments, in addition to a need for reducing the exposure of the moving mechanical elements of the system to the elements.
Accordingly, it is primary object of the present invention to provide a compact train positioning system that can be used in situations of close horizontal track clearance.
It is a further object of the present invention to provide a low clearance train positioning system that uses vertically operating dogs to engage the bogey frame of a car in conjunction with a over/under vertical disposed chain drive.
A still further object of the present invention is to provide a low clearance train positioning system that is a reversing system utilizing spaced opposed dogs.
Another object of the present invention is to provide a low clearance train positioning system that includes a top rail and lower chain tube enclosure.
Other objects and advantages associated with the present invention will reveal themselves or become apparent to those skilled in the art upon familiarization with the specification, drawings and claims contained herein.
The present invention provides a low clearance, compact guideway, train positioning system that can be installed in close quarters alongside an existing railroad track. The system is chain driven and features an improved over/under or vertical sprocket carriage drive system in which parts normally exposed to the elements are protected while, at the same time, horizontal space requirements alongside the track are reduced. The system employs a vertically oriented chain drive which employs enclosed vertically mounted drive and idler sprocket units and a chain tube enclosing the lower chain strand which further minimizes exposure of the mechanism chain to the elements by totally enclosing the lower chain path in the over/under arrangement. In this manner, the tendency of the mechanism including the chain and sprockets to accumulate foreign material and debris during and between uses causing wear and increased maintenance costs is averted.
The system is installed and operates closely alongside and parallel to the track using carriage-mounted, horizontally pivoting, bogey wheel frame-engaging high or low dogs that engage and advance railcars using successive car bogey frames in a well known manner. The dog carriage may be of a low profile, preferably not protruding more than a few inches above the level of the pivot mounting shafts for the dogs.
The train positioning or progressing system of the detailed description is a concurrent low dog designed to move a string of empty railcars and includes left and right low dog indexers or progressors which operate together to advance the cars as they reciprocate together along the tracks, alternating between a seeking/power or pulling mode and a redeploying mode. Of course, the arrangement of the invention may be used with any continuous chain drive system. The train positioning or progressing system may be designed to operate in a single direction or may be made reversing using spaced opposed dogs on separate carriages designed to collapse or raise in a conventional manner. The dogs are constructed to pivot or be locked down in the seeking mode (retracting direction) and pull or push the bogey wheel frame in the opposing direction during positioning. Construction and operation of the dogs is conventional and known to those skilled in the art. Reference is also made to the documents incorporated by reference herein.
The dog carriages of each indexer of the train positioning system of the present invention are spaced a fixed distance apart and slidably engaged in a dog carriage indexer track or guideway situated alongside and closely paralleling the railroad track. Each outer end of the spaced dog carriages is connected to a drive chain which meshes with a drive sprocket at one end of the indexer track and an idler pulley or sprocket at the other end of the indexer or track or guideway. The inner ends of the spaced dog carriages are connected together by a carriage-connecting chain and hydraulic tensioning cylinder which operates to keep the chain loop taut and the space between the carriages fixed. The drive sprocket is preferably aligned with the guideway and is generally powered by a prime mover, preferably a hydraulic motor. The hydraulic motors are operated together by a single combined hydraulic system to advance the drive chain to move the indexers in unison in either direction along the track.
Construction and operation of the dogs may be conventional and with respect to the detection of the presence of wheels and/or bogey frame on the cars of interest, of course, any compatible system may be employed. This includes proximity detection devices, optical beam systems and back deflection of the dogs themselves. Pull-down shafts and trippers may also be employed, together with proximity devices, noting carriage position, examples of which are shown in co-pending U.S. application Ser. No. 09/546,984, filed Apr. 11, 2000 and assigned to the same Assignee as the present application. This document is deemed incorporated herein by reference for any purpose.